a hobby horse

hobby-horse

A subject, topic, or issue about which one frequently or incessantly talks, expounds, or complains. Ah, here we go again. Once grandpa gets on his hobby-horse about the government, there's no stopping him!

a ˈhobby horse

a subject that somebody feels strongly about and likes to talk about: Sorry, I’m starting to get on my hobby horse! (= talk about my favourite subject).
See also: hobby, horse
References in periodicals archive ?
Crude in nature, this toy mimicked the back of a horse better than a hobby horse.
There are numerous videos on YouTube about how to make a hobby horse, and the components are easy to find: a broomstick, fabric, fur, wool, stuffing and decorations - which are obviously up to each creator.
When the son emerges it is to ask grandma if she remembers making him a hobby horse when he was small.
* A hobby horse pattern (Cut out the hobby horse shown here.
For example, George Tollet, from his retirement at Betley Hall in Staffordshire, contributed to the 1778 Johnson-Steevens edition a long note describing stained glass figures of morris dancers, Maid Marion, a hobby horse and a Maypole.